Process for extracting dye from textiles

ABSTRACT

A PROCESS FOR REDUCING OR ELIMINATING THE DESPERSED DYE CONTENT OF POLYESTER TEXTILE MATERIALS INCLUDES EXPOSING THE MATERIAL TO VAPOR AND/OR LIQUID PHASE SOLVENT, PREFERABLY METHYLENE CHLORIDE. IN ACCORDANCE WITH ONE ASPECT OF THE INVENTION, THE MATERIAL IS IRRADIATED DURING TREATMENT TO DERIVE SYNERGISTIC COACTION BETWEEN THE DYE ELIMINATION FUNCTIONING OF THE SOLVENT AND THE RADIATION.

' April 23, 1974 s. LEWKOWITZ ET AL PROCESS FOR EXI'IRAC'IING 1m: FROM TEXTILES Filed May 4, 1972 souncs OF RADIATION CONDENSER EVAPORATOR l DYE COL L EC TION STATION United States Patent Office 3,806,316 PROCESS FOR EXTRACTING DYE FROM TEXTILES Steven Lewkowitz, Bronx, N.Y., and Bruce S. Bernstein, Somerville, Sevram A. Harem, Jr., Mountain Lakes, and Martin A. Welt, Morris Plains, N.J., assignors to Radiation Technology, Inc., Rockaway N.J., and Scientific Textile Systems, Inc., East Rutherford, NJ., fractional part interest to each Filed May 4, 1972, Ser. No. 250,124 Int. Cl. D06] 3/04 US. Cl. 8--103 6 Claims ABSTRACT OF THE DISCLOSURE A process for reducing or eliminating the disperse dye content of polyester textile materials includes exposing the material to vapor and/or liquid phase solvent, preferably methylene chloride. In accordance with one aspect of the invention, the material is irradiated during treatment to derive synergistic coaction between the dye elimination functioning of the solvent and the radiation.

This invention relates to textile processing and, more specifically, to the removal or reduction in the dye content of fabrics, filaments or the like.

Those concerned with the production and sale of textile products have long desired to remove or reduce the dye content of selected fabrics on occasion. For example, many colors are integrally associated with a particular fashion cycle. Accordingly, fabrics dyed this color, or color pattern, are often unsaleable for any significant purpose after the corresponding fashion vogue dissipates. Also variations between dye lots give rise to variations in color for dyed goods, some variations being so pronounced as to render the goods unsuitable for their intended use.

However, a reliable and economically realistic process for effecting dye reduction or color elimantion to render fibers useful per se, or redyeable to a desired color has heretofore not been available.

It is thus an object of the present invention to provide an improved process for color extraction from textiles.

More specifically, an object of the present invention is the provision of a color reduction or elimination process for textiles which is reliable and economically competitive, which does not injure the fiber or fabric being treated; and which renders the processed fabric amenable to redyeing when desired.

The above and other objects of the present invention are realized in a specific, illustrative process for removing coloring, e.g., disperse dyes, from a fabric (e.g., of polyester). The dyed fabric is exposed to liquid and/or vaporous methylene chloride, optionally in the presence of nuclear radiation. The methylene chloride causes the fabric to release its dye content, the time rate of dye reduction being increased in a synergistic manner in the presence of radiation.

The above and other features and advantages of the present invention are realized in a specific, illustrative process for reducing the dye content of textiles, which is described hereinbelow in conjunction with the accompanying drawing.

Referring now to the drawing, there is shown a chamber 10 having disposed therein a bolt of fabric rolled onto a core 33 having perforations 34 therein. The bolt and core 15-33 are suspended from the sides of the chamber 10 by an axle rod 30 and spokes 31. The axle 30 may be rotationally driven if desired. Also, the axle 30 may support plural cascaded fabric packages or bolts along the length of the chamber 10, and several chambers may be employed. The fabric 15 is initially characterized 3,806,316 Patented Apr. 23, 1974 by a dyed coloring which is unsuitable for the intended fabric end use, it being desired to reduce the dye content to lighten the fiber color or to eliminate all color to render the fabric suitable for redyeing.

A solvent 12. in the chamber 10 is heated by a heat source 19. As discussed hereinbelow, the solvent coac'ts with the fabric for expelling the fabric dye content, the absolute dyg 'dontent remaining in the chamber being an inverse function of the elapsed exposure time.

An evaporator 26 extracts fluid from the bottom of the chamber 10, evaporating the solvent and passing the dye expelled from the fabric, liquid at the solvent boiling point (e.g., 39.5 :5 C. for methylene chloride), to a dye collection station 28. The vaporized solvent, collected from the top of the chamber 10 and from the evaporator 26, is condensed by a condenser 24 and returned to the solvent pool in the chamber 10.

Finally, a source of nuclear radiation 32, for example, gamma radiation from a cobalt 60 source, may be provided and directed at the fabric.

In accordance with differing aspects of the present invention, and as described more fully below, dye may be removed from a dyed fabric 15 by exposing the fabric (or thread) to radiation in the absence of any solvent; and by exposing the fabric to an appropriate solvent in vapor and/or liquid phase-as by immersing the fabric 15 in the solution as shown in the drawing-both in the presence and absence of radiation from the source 32. Where both solvent and radiation are employed, a significant synergistic benefit is derived, i.e., the color fading time is much reduced compared with the use of solvent alone, and the radiation dosage is only a small percentage of that required to expel dye by radiation alone. Further, in some instances, dye elimination is possible only when both radiation and a solventare employed.

Moreover, radiation has the further salutory effect of eliminating or reducing the dye coloration of the solvent, hence increasing the dye-leaching eflicacy of the solvent. When directed at the solvent alone (i.e., in the absence of the dyed textiles), radiation serves to reclaim the methylene chloride solvent carrier.

In particular, specific examples are presented hereinbelow depicting operation of the present invention to reduce and/or eliminate the disperse dye content of polyester fabrics. As a general matter, a polyester may be characterized as condensation polymer of a polyfunctional acid and a polyfunctional alcohol.

Polyester fibers have traditionally been very difiicult to dye. This has been attributed to the lack of hydrophilic properties and of reactive groups, such as are present in cellulosic and proteinaceous fibers. This difliculty can be overcome by using dispersed dyes, which are applied from aqueous dispersion, and which have greater afiinity for the fiber than for the water of the dye-bath. The dyes therefore migrate to the fiber region, and form a solid solution around it. It is best to use small dyestuff molecules at elevated temperatures. Even the disperse dyeing technique is rather difficult to employ successfully with polyesters, due to the high orientation and tight packing of the polymeric chains; certain special techniques must be used, as described below:

(a) A carrier aids the dyeing process; a carrier is essentially a swelling agent that enhances chain movement and allows the dye to reach regions of the fiber that would normally not be accessible in its absence. When a small quantity is used in the dyebath, interchain distances can be increased slightly. Examples of carriers include butyl benzoate, trichlorobenzene, and o-phenyl phenol. It is not always necessary to use high pressure when carriers are present, although that may be desirable in some cases.

('b) High temperature (and pressure) also serves to increase the interchain distance to some extent, thus allowing easier dyeing. Under pressure, temperatures at about 120 C. are generally satisfactory. Accordingly, most polyester fabrics and yarns are dyed by disperse dye technique.

Specific examples for treating polyester materials which contain disperse dyes in accordance with the principles of the present invention are as follows:

EXAMPLE 1 Dacron 56 (understood to be a terephthalic acid-ethylene glycol condensation polymer) initially included a green disperse dye applied to the fabric at 210 F. The dye carrier was a Carolid (trademark of the Tanatex Corporation of New Jersey) type carrier used in a gram per liter concentration.

The above described dye polyester was directly immersed in boiling methylene chloride at a ratio 1.85 grams of cloth to 150 grams of solvent (a ratio of approximately 80:1). The material underwent three solvent cycles, i.e., immersion periods of one hour in the boiling methylene chloride which was changed and regenerated at the end of each cycle.

At the conclusion of its treatment, the material had turned to white, while retaining its original hand, i.e., its texture and physical properties to an artisan in the fabric field.

EXAMPLE 2 A Kodel 400 textured fabric (understood to be polyethylene terephthalate) included therein a disperse dye system formed of Eastman polyester yellow GLW (2.50%); Eastman polyester red FFBL (0. 68%); Eastman polyester blue BLF (0.61%); Latyl Carrier LF (dimethylterephthalate) (4.00%); and Versene 100 as a sequestering agent 1%). The dye solution was adjusted to a pH of 5.0 with acetic acid in a bath ratio of :1. The dye was applied under pressure for one hour at 250 F. in a jet machine.

Boiling methylene chloride in a ratio of 1.85 grams of cloth to 150 grams of solvent was applied for three cycles all as set forth in particular detail in Example 1.

At the conclusion of its treatment, the Kodel polyester had turned to white retaining its hand.

EXAMPLE 3 Kodel type 411 polyester, heat set at 420 F. prior to dyeing, initially had a disperse dye coloration formed of Eastman polyester scarlet Y (2%); Dysyn 1627 (trichlorobenzene and butyl benzoate) (4%); Versene 100 (sequestering agent) (1% The dye solution was adjusted to a pH of 5.0 with acetic acid in a bath ratio of 15:1. The dye was applied under pressure for one hour at 250 F. in a jet machine.

The material was directly immersed in the methylene chloride all as more particularly set forth in Example 1. At the conclusion of its treatment the material had turned pure white without loss of hand.

EXAMPLE 4 A spun Dacron polyester filament initially contained a green disperse dye applied in a jet machine under pressure for one hour at 250 F. The dye included a 3% Dysyn carrier.

After three cycles of direct immersion in the boiling methylene chloride solution, the filament had turned pure white without impairment of its physical properties.

EXAMPLE 5 A Dacron type of polyester material, produced by I Olympia Mills, Tuscaloosa, Ala. was initially colored with a purple dye applied by the dispersion process.

The material was exposed to methylene chloride in Soxhlet extraction apparatus. After one Soxhlet cycle (a period between and minutes), the purple dye became very light and, upon the completion of two cycles,

EXAMPLE 6- The Dacron polyester material of Example 5 was directly immersed in methylene chloride solvent (at room temperature) at the :1 fabric-solvent ratio. Cobalt 60 gamma radiation was coincidentally applied to the specimen to a dose of one megarad at a rate of .035 megarad per hour. The sample turned white.

EXAMPLE 7 The Dacron polyester specimen of Example 5 with the purple disperse dye was treated in the Soxhlet extraction apparatus, the solvent being chlorobenzene at the approximate 80:1 solvent ratio. The material remained purple at the condusion of one Soxhlet cycle and became white after two such cycles. However, the processed materials had a changed hand, becoming stiffer and harsher to the touch.

EXAMPLE 8 The same material as set forth in Example 5 underwent the treatment of Example 7, except that Cobalt 60 gamma radiation of a dose of one megarad was applied at a field rate of .035 megarads per hour, and the original methylene chloride solvent was not changed. The material turned white with the changed hand.

EXAMPLE 9 The Dacron polyester material of Example 5, with the purple disperse dye, was immersed in methylene chloride solvent (at room temperature) in the ratio 3.70 grams of cloth to 75 grams of solvent (in approximate 20:1 ratio). A radiation dose of one megarad at a field rate of .035 megarads per hour was applied. The material turned to light purple.

EXAMPLE 10 We repeat here the substance of Example 9, except that a ratio of 3.70 grams of cloth to grams of solvent (approximately 40:1) was employed. The material became white.

EXAMPLE 11 The material of Example 5, with the purple disperse dye, was directly immersed in the boiling methylene chloride at the 80:1 cloth-solvent ratio. A radiation dose of 0.56 megarads was applied at a field rate of .035 megarads per hour, and the material turned white. were investigated with the results indicated:

EXAMPLE 12 Two specimens of blue polyester fabric were exposed to 0.6 and 1.3 megarad doses in a 0.6 megarad field, respectively. The former specimen retained some color, while the latter, more heavily exposed specimen turned white.

As a general matter, the solvent where radiation is used is essentially uncolored at the end of processing, whereas simple immersion or Soxhlet extraction yields a deeply colored solvent which must be distilled for purification.

EXAMPLE 13 A dyed polyester fabric was exposed to nuclear radiation, total doses of between 34.3 and 198.7 megarads being employed, in fields ranging from 0.75 to 2.75 megarads per hour, to effect varying degrees of color reduction to complete color elimination.

In addition to the foregoing examples, polyester blends were investigated with the results indicated:

(1) Dacron (polyester) /Avri1 (oellulosic) (65/35) was initially green, and was directly immersed in heated methylene chloride. The dye was eliminated from the polyester portion of the fabric, .but not from the Avril.

(2) The same results obtained, for like processing in:

Mullen burst strength (lbs) Color Before After Material Initial Final process process Fortrel Pink White 200=l=2 180==2 Dacron Blue do 160:1;4 140:1:5 o Green. do l81=l=1 173:1:2

Methylene chloride has thus been found to comprise an especially efifective solvent. Also, the synergistic effect of methylene chloride and irradiation is amply demon strated in these examples.

We have not as yet identified the particular mechanism giving rise to extraction of the dye from the fabric (or fiber) for the processes involving a solvent. By way of explanation and not limitation, experimental evidence (the separability of the collected dye and the solvent) indicates that the dye extraction is by a physical process rather than a chemical reaction. This physical process is postulated to be a swelling of the polyester fibers or intercrystalline regions to release mechanically entrapped dye particles and/or dye held by Vander Walls or related forces.

Further, dyed cellulose acetate (e.g., rayon) has been faded by exposing the material to vaporous (and condensed liquid phase) methyl alcohol. The solvents useful for extracting dye from polyester were unsuitable for the cellulose acetate since they dissolved the actate material.

It is to be understood that the above-described dye extraction operations are merely illustrative of the principles of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope thereof. For example, a vapor phase solvent system (or a liquid-vapor mixture) may be utilized.

What is claimed is:

1. The process of removing dye coloring from polyester textiles comprising exposing said textile to cobalt nuclear radiation.

2. A process as in claim 1 further comprising the step of immersing said polyester in methylene chloride coincident with radiation.

3. A process as in claim 1 further comprising the step of exposing said polyester to vapor phase methylene chloride solvent coincident with said radiation.

4. The process of removing dye from a polyester material in an operative dye elimination volume, the improvement comprising the step of immersing said ma terial in methylene chloride in said dye elimination volume, wherein said solvent is in liquid and vapor form.

5. A process as in claim 4, further comprising the step of directing cobalt irradiation at said textile material.

6. A method for reclaiming dye laden methylene chloride, the improvement comprising exposing said dye laden methylene chloride to cobalt nuclear irradiation.

References Cited UNITED STATES PATENTS 2,235,234 3/1941 Moncrielf .881 1,791,990 4/1931 Whitehead 8102 FOREIGN PATENTS 668,869 12/1938 Germany 8-103 MAYER WEINBLATI, Primary Examiner US. Cl. X.R. 8-80, 81, 102 

